The present invention relates to a securing device for sports shoes.
Particularly as regards ski boots, the problem of securing the region of the heel or instep of the foot so as to allow optimum transmission of forces from the leg to the ski while skiing is strongly felt.
Several devices are known for this purpose; for example U.S. Pat. No. 4,615,127 discloses a boot having a flexible flap at the rear part of the shell; the flexible flap interacts with pressure means. The pressure means are associated at the rear quarter and are constituted by a knob the rotation whereof pushes an adapted presser toward the flap.
This solution has a considerable drawback: a region of highly localized pressure is in fact created, causing considerable discomfort to the user, since a tendon subject to continuous contraction and relaxation is affected at this region.
Furthermore, the described use of a pair of wings arranged transversely to the flap, which can be moved mutually closer by means of an adapted screw, does not solve the problem, since said wings deform the flap, which is thus subject to breakage; the same is true for the rear quarter, since it is affected by the action of the screw.
Furthermore the assembly of the device on the boot is difficult.
Another important drawback is constituted by the fact that the stiffness of the wings, which is linked to the fact that they are located in a region adjacent to the malleoli, consequently requiring them to have a modest longitudinal extension, causes discomfort for particular anatomical configurations of the foot, since it has been observed that the free ends of the wings cause localized pressure regions as they are unable to embrace the entire affected region of the foot by following its anatomical shape.
U.S. Pat. No. 5,020,248 discloses a ski boot which comprises an adjustable foot support located in the heel region. The support is constituted by a U-shaped spring having a base located in the region of the heel and of the shell and having wings extending inside the shell. The wings can be adjusted with respect to one another by using a screw which is rotatably associated, transversely to the shell and is provided with a right-handed and left-handed threaded stem for the axial movement of appropriate washers.
This known solution has some drawbacks: on one hand, it requires a particular coupling of the springs and of the screw to the shell. Furthermore, the compression applied at the wings causes the wings to deform approximately at the base, while the free ends remain adjacent to the internal surface of the shell. This means that a localized pressure region is produced in the rear region of the heel; this pressure tends to push the foot forward, thus securing it by virtue of the interaction of its instep at the shell.
The foot is thus not secured in its natural position but is pushed and secured by interaction with the shell.
Austrian patent application no. 1130/85, dated Apr. 16, 1985 discloses a heel securing device which consists of a piece of lining which is arranged between a shell and an innerboot. The lining can be adjusted with the aid of a screw adjustment device and crosses the shell at the heel region at least longitudinally to the boot.
The piece of lining has two flaps which laterally surround the foot. The flaps divide in the direction of the innerboot and are provided with flexible portions. The adjustment screw acts on two positioning arms which adhere to the flaps of the piece of lining from outside.
The securing device operates at the innerboot and interacts with pivots which are pivoted at adapted protrusions which protrude inside the quarter. It is therefore considerably difficult to obtain these seats and consequently difficult to assembly the boot.
One also observes the possibility of deformation of the innerboots which, being localized, can lead to breakages, as well as of a possible deformation of the quarter due to the presence of the pivots.
Finally, it is noted that since the device affects the region adjacent to the malleoli, it tends to substantially narrow the innerboot, which compresses the foot in the direction of the tip of the shell, so that one obtains not so much a securing of the foot in its natural position as a securing of said foot by interaction with the shell.
Furthermore, the presence of the stem of the screw behind the upper region of the heel constitutes, since said stem is rigid, a factor of considerable discomfort for the user, because it interacts at a region of the foot which is affected by a tendon which contracts and extends.